The present invention relates to the valve gear of an internal combustion engine; and, specifically relates to mechanisms of the type known as "valve selectors", which are devices selectively operable to render totally or partially inoperative and normally operative, the combustion chamber valves of an engine. Examples of such devices are known and described as, for example, in "AUTOMOTIVE ENGINEERING", Vol. 85, No. 5, at page 30, May 1977, published by the Society of Automotive Engineers, 400 Commonwealth Drive, Warrendale, Pennsylvania 15096.
The aforementioned known device for permitting disabling and enabling of the engine valve gear while the engine is running, has been applied to valve gear of the type having individual rocker arms pivotally mounted by means of an individual rocker pivot stanchion provided on the cylinder head of the engine. This has been accomplished by providing a latchable mechanism which is movable to permit a rocker fulcrum received over the mounting stanchion to be moved therealong. Movement of the fulcrum changes the location of the rocker arm pivot and effects the pivotal motion of the rocker arm in the valve gear, resulting in changes in the manner in which the rocker arm receives and transmits to the associated valve the cyclically applied valve gear driving forces.
The latchable means is movable between a plurality of positions which permit the relocation of the rocker arm pivot fulcrum. In the operation of such a device, when it is desired to disable or re-enable the selected valves, an actuator applies and holds an actuating force on the latchable means which moves between the different positions only when the valve gear driving forces are relaxed. The latchable means is latched in the selected position upon cyclic reapplication of the valve gear driving forces. In the enabling position, the latchable means positions the fulcrum such that the rocker pivots thereabout to effect normal valve opening and closing. In the disabling position the latchable means is operative to provide lost-motion in the valve gear whereby pivotal movement of the rocker, upon cyclic application of the valve gear forces, is not effective to open the selected valves.
It will be readily understood to those familiar with internal combustion engines having overhead type valve gear, that such a valve selector mechanism is readily adaptable to engines having each valve rocker arm fulcrum mounted on individual studs or stanchions. However, a substantial number of internal combustion engines utilize valve gear in which the valve rocker arms are pivotally received over a common shaft, usually running the length of a bank of cylinders. In this type of valve gear arrangement, the shaft is attached to the cylinder head in a manner preventing movement of the shaft and each of the rocker arms have a bore therein which registers in sliding engagement over the outer periphery of the shaft. It will be apparent that the shaft-mounted rocker type valve gear does not readily lend itself to incorporation of a latchable means for permitting selective location of the rocker arm pivot, since the rocker shaft is the fulcrum for each of the rocker arms in the entire bank of combustion chambers or cylinders.
For this reason, it has been desired to find a way in which the valve selector type disabling and re-enabling mechanism could be employed in multi-chambered engines of the type having overhead valve gear with rocker arms mounted on a common shaft for the chambers in each bank. In particular, it has been desired to find a way to incorporate valve selectors in the valve gear of a rocker-shaft type without requiring redesign or reworking of the rocker shaft mounting stanchions and the consequent re-tooling for manufacturing the cylinder heads of such engines.